Engineering Commons^™

College Of Engineering Senior Design Competition Spring 2007, University Of Nevada, Las Vegas

Fred and Harriet Cox Senior Design Competition Projects

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge.

The senior design competition helps to focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects …

Optimal Placement Of Metal Foils In Ultrasonic Consolidation Process, Raji Rexavier

All Theses

Ultrasonic Consolidation is a combination of additive and subtractive
manufacturing processes resulting in considerable material waste. This waste is a
function of the geometry of the part being manufactured and of the relative
placement of the layer with respect to the metal bands. Thus the waste may be
minimized by careful choice of the layer angle and offset from the original
position.
Previous work done in this field had developed an automated algorithm which
optimally places and orients the individual slices of the STL file of the artifact
being manufactured. However, the problem was solved on a 2-D scale and …

Analysis Of Ride Quality Of Tractor Semi-Trailers, Christopher Spivey

All Theses

This thesis develops parameter variation techniques for calculating the set of vehicle parameters that result in the best ride comfort for the driver. The model is a fifteen degree-of-freedom (15 DOF) tractor semi-trailer vertical dynamic ride model. The modeling and simulation techniques used in this thesis are extensions of the research performed by Trangsrud and Vaduri. Features of the model include suspension characteristics for (a) each of the five axles (tractor steer axle, two tractor drive axles, and two trailer axles), (b) tires, (c) a flexible engine mount, (d) the tractor cab, (e) the driver's seat, and (f) a fifth …

Real Time Prognostic Strategies Application To Gas Turbines, Rajat Sekhon

All Theses

Gas turbines are increasingly deployed throughout the world to provide electrical and mechanical power in consumer and industrial sectors. The efficiency of these complex multi-domain systems is dependant on the turbine's design, established operating envelope, environmental conditions, and maintenance schedule. A real-time health management strategy can enhance overall plant reliability through the continual monitoring of transient and steady-state system operations. The availability of sensory information for control system needs often allow diagnostic/prognostic algorithms to be executed in a parallel fashion which warn of impending system degradations. Specifically, prognostic strategies estimate the future plant behavior which leads to minimized maintenance costs …

Design Of A Controller For A Precision Positioning Machine, Joshua Tarbutton

All Theses

System identification was used to build an accurate model of a high-precision measurement system. The model built by system identification was compared to modeling by first laws and showed extremely similar results. Pole-placement control design based on the identified system was used to place the systems' dominant poles. The necessary gains to achieve the desired system response were determined by using the identified model and knowledge of the controller structure. The performance of the model-based controller was compared to actual data of the system and showed that control based on the identified model can be used to accurately control the …

Temperature Control Of An Air Shower, Vedik Bobba

All Theses

Accuracy and repeatability in measurement is a primary concern in improving and maintaining the quality of a product in an industry. In the case of coordinate measuring machines, these factors are affected due to the ambient conditions. Specifically, change in temperature affects machine geometry and causes positioning errors. As a result, temperature and humidity control inside the housing has become an important and integrated concern of measuring machine. This research concentrates on the modeling, design, control and validation of an air shower to meet a 20 ± 0.1 ¼C specification.
The optimum performance of the control of temperature of air …

Energy Absorption Of Sine Wave Beams Subjected To Axial Impact Loading, Robert Smith

All Theses

Energy absorbers ideally remove kinetic energy efficiently and reliably while minimizing force magnitudes felt on the moving body. Until now, energy absorber design has concentrated on thin-walled prismatic tubes and tapered tubes. Sine wave beams (SWB) have been previously investigated as energy absorbers under lateral impacting situations only. This thesis investigates the energy absorption of the SWB under axial impact. FE models simulated the energy absorbing response of the SWB. Parametric analyses were performed using the structure's thickness, the web amplitude, and the period number of the web. The SWB's performance is evaluated and then compared to the prismatic structures. …

Modeling Requirements Propagation To Generate Solutions For Minimizing Mass, Thulasiram Ezhilan

All Theses

This thesis investigates the issue of weight reduction in moderately complex systems by addressing how to cascade the requirements to the individual components. Though mass can be reduced using different techniques such as material substitution or structural optimization; a systematic method for allocating mass as a function of requirements is necessary to provide novel alternate solutions that enable reduction of mass of the system while satisfying the requirements and tests governing them. Such a method can be developed by exploring different aspects of achieving weight reduction through change propagation in the parameters/elements governing the system. Though efforts have been made …

Machinability And Microstructure Stability During The Machining Of Pure Copper And Titanium Processed By Equal Channel Angular Pressing, Mason Morehead

All Theses

For ultrafine grained materials (containing microstructures of 100-300 nm) to be manufactured and used in industry, machining research is needed to form and shape these materials into their final dimensions. Because of their high internal energy, UFG materials are known to have microstructures which are susceptible to undesirable changes at low temperatures. In this study, pure ultrafine grained copper and titanium as well as their respective coarse grained (CG) counterparts were tested for their relative machinability and microstructure stability through lathe turning. To evaluate the machinability cutting forces, tool wear, chip morphology, and surface roughness were studied using different cutting …

A Study Of Induced Drag And Spanwise Lift Distribution For Three-Dimensional Inviscid Flow Over A Wing, Scott Monsch

All Theses

Numerical results for an untwisted, finite rectangular wing (NACA 0012, AR = 6.7) using no flap deflections are compared against theoretical lifting line predictions. The numerical approach used an Euler-based computational fluid dynamic (CFD) solver. A span-wise lift distribution was extracted from the CFD solution. The comparison between the predicted numerical and lifting-line span-wise lift distributions shows good agreement with a maximum deviation of only 2.4% over the wing span.
The induced drag was extracted from the downstream wake using a wake integral technique referred to as Trefftz plane analysis. The predictions for induced drag based on surface integration, wake …

Tension-Compression Fatigue Behavior Of A Carbon Fiber/Epoxy (Im7/Epon 862) Composite Fabricated Using Vacuum Assisted Resin Transfer Molding Process, David W. Katwyk

Theses and Dissertations

New composite materials and processing methods are continually being developed for use in high performance aerospace systems. One of these new processing methods is the vacuum assisted resin transfer molding (VARTM) process, which shows promise in producing large structural components that have good properties at a lower cost than traditional manufacturing methods. Future widespread use of components manufactured using the VARTM process depends on understanding how these components perform under service conditions, specifically under impact and fatigue conditions. The tension-compression fatigue behavior of a four-harness satin weave carbon fiber/epoxy (IM7/EPON 862) composite manufactured using the VARTM process is investigated in …

An Evaluation Of High Velocity Wear, Gregory J. Cameron

Theses and Dissertations

The Holloman High Speed Test Track (HHSTT) is a rocket-powered sled track facility used for testing a variety of hypervelocity aerospace applications. The current speed record is 6,453 miles per hour. While this seems fast there are customers at the track that have requirements demanding even faster speeds. Significant research has been conducted in the area of rail gouging as it relates to the test track, and efforts are under way to reduce and even eliminate this phenomenon. Any steps taken in this effort may eliminate catastrophic sled failures caused by gouging, however wear is another damaging issue that needs …

Damage Detection Using Lamb Waves For Structural Health Monitoring, Jeffrey S. Crider Ii

Theses and Dissertations

Nondestructive structural health monitoring (SHM) is an evolving technology being developed for monitoring air and space systems. The information gathered on a system's structural integrity through SHM detection methods may result in reduced costly maintenance inspections, enhanced safety, and system failure predictions. This study evaluates Lamb wave approaches used to detect simulated cracks in laboratory experiments on thin plates to detect more realistic damage in a test article representing the complex geometry of an existing aircraft bulkhead. We take a "hot-spot" monitoring approach, where we monitor an area of the structure known to fail. In our experiment, we evaluated the …

Experimental Methods To Characterize Nonlinear Vibration Of Flapping Wing Micro Air Vehicles, Adam P. Tobias

Theses and Dissertations

For urban combat reconnaissance, the flapping wing micro air vehicle concept is ideal because of its low speed and miniature size, which are both conducive to indoor operations. The focus of this research is the development of experimental methods best suited for the vibration testing of the wing structure of a flapping wing micro air vehicle. This study utilizes the similarity of a beam resonating at its first bending mode to actual wing flapping motion. While computational finite element analysis based on linear vibration theory is employed for preliminary beam sizing, an emphasis is placed on experimental measurement of the …

Lamb Wave Propagation In Varying Thermal Environments, Jennifer P. Andrews

Theses and Dissertations

During flight, launch, and reentry, external surfaces on aerospace vehicles undergo extreme thermo-acoustic loads resulting in structural degradation. Structural health monitoring techniques are being devised to evaluate the health of these structures by locating and quantifying structural damage during and after flight. One such technique uses Lamb wave propagation to assess damage on the surface and through the thickness of thin materials. The objective of this study was to assess the sensitivity of piezo-generated Lamb wave propagation to isothermal and thermal gradient environments using both theoretical and experimental methods. Experimental isothermal tests were conducted over a temperature range of 0-225 …

The Effects Of Microstructure On Fretting Fatigue Behavior Of Nickel Alloy In-100, Erik C. Saladin

Theses and Dissertations

This thesis studied the effect of microstructure on the fretting fatigue behavior of IN-100. First, fretting and plain fatigue S-N curves were determined over a large range of applied stress at an identical R-ratio and for fretting tests, done with a constant contact load. It was found that fretting fatigue reduces the cycles to failure compared to plain fatigue. The half contact width was found for the specimens, the crack initiation angle was found to be 40 deg and the crack initiation location was at the trailing edge of contact for the fretting specimens. Computational work included finding the stress …

Effects Of Prior Aging At Elevated Temperature In Air And In Argon Environments On Creep Response Of Pmr-15 Neat Resin, Joseph L. Broeckert

Theses and Dissertations

Creep behavior of PMR-15 neat resin, a polyimide thermoset polymer, aged in air or argon gaseous environments at 288 °C for up to 1000 h was evaluated. Creep tests were performed at 288 C at creep stress levels of 20 and 10 MPa. Creep periods of at least 25 h in duration were followed by recovery at zero stress. Weight loss and growth of the oxidation layer were also monitored and correlated with aging time. The aging time in both air and argon environments had a strong influence on the creep and recovery response of PMR-15 neat resin. Samples aged …

Preparation And Lithium Storage Performance Of Nano-Structural Sno2/Carbon Nanotubes Composite Electrodes, Hong-Bing Wei, Ling Huang, Xiao-Bin Wu, Fu-Sheng Ke, Jin-Shu Cai, Xiao-Yong Fan, Fang-Zu Yang, Shi-Gang Sun

Journal of Electrochemistry

The Nano-structural SnO₂/Carbon Nanotubes Composites were prepared in a solution of SnCl₂,ethylene glycol(EG),purified MWCNTs and sodium dodecyl sulfate(SDS) at 160 ℃.The phase structure and surface morphology of the composites were measured by XRD HRTEM and SEM.The results indicate that there are high dispersions and high loadings of SnO₂ nanoparticles on MWCNTs.Electrochemical lithium storage performance was studied preliminarily on the obtained samples.MWCNTs modified with SnO₂ nanoparicles were shown to have a higher electrochemical reversible capacity than that of MWCNTs during the charge and discharge process.MWCNTs can accommodate the larger structure strain of the active materials …

The Influence Of Electrolytic Conditions On Synthesis Of Feo42-, Yan Zhou, Wei-Hua Yang, Dong-Qin Bi, Ting-Ting Huang, Zhen Sun, Quan-Feng Guo

Journal of Electrochemistry

The FeO₄^2-was synthesized using iron lattice as anode and the solid K₂FeO₄ was also prepared.Influence of electrolytic conditions,such as stir,ultrasonic,temperature and current density on the current efficiency were studied.The results showed that preferable ferrate(VI) current yield was obtained in a current density of 10 mA·cm^-2,temperature 30 ℃ and 14 mol/L NaOH as electrolyte under at stirring effect.

Variable Frequence Switching Power Supply Used To Aluminum Foil Corrosion, Xiang-Dong Zhuo, Lan Sun, Guo-Qing Qian, Chang-Jian Lin

Journal of Electrochemistry

A new variable frequence and multi-wave power supply used to aluminum foil corrosion is introduced. The switching supply power supply controlled by the microcontroller and Variable Frequence in low band and multi-wave, big power supply controlled by the electronic switch bridge for changing phase were designed. This power supply does not need bulky and cumbersome transformer, and the frequency at lower limit is not limited, even lower than 1Hz.

Effects Of Direct Current Bias Potentials On Lipid Membranes Forming On A Glassy Carbon Electrode, Yu-Hui Li, Hong-Wei Zhang, Gui-Lan Song, Zhan-Jun Zhang, Sheng-Min Cai

Journal of Electrochemistry

The effects of direct current(DC) bias voltage on the structure of lipid membranes forming on a glassy carbon electrode(GCE) was investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS).The experiment showed that the lipid membranes can be formed with either positive or negative bias potential exerted.When bias voltage was exerted,bilayer lipid membranes tended to form due to the electrostatic interaction between the superficial positive charges on the polarized electrode and the negative charged part of PC.When the positive bias voltage overrun the range,the lacunas on s-BLMs would increase,and the BLMs would be broken.A proper equivalent circuit was nonlinearly fitted,based on the …

Composite Electroplating And Characterizations Of Sn-Sba15 Anode For Lithium-Ion Batteries, Xiao-Yong Fan, Jin-Mei Xu, Quan-Chao Zhuang, Hong-Hong Jiang, Ling Huang, Yan-Xia Jiang, Quan-Feng Dong, Shi-Gang Sun

Journal of Electrochemistry

Sn-SBA15 anode was prepared by composite electroplating. The first discharge and charge capacity was 1075mAh/g and 630mAh/g respectively. After fifty charge/discharge cycles, the charge and discharge capacity of Sn-SBA15 were retained above 400mAh/g. XRD patterns indicated that the Sn-SBA15 has tetragonal crystal type. SEM images showed that the Sn-SBA15 had a honeycombed surface. EIS results indicated that there was SEI film formed on the surface of Sn-SBA15 electrode.

Electrochemical Oxidation Of The Phenol In The Chloride System, Yong Liu, Dan Liu, Shi-Lin Zhao, Jing-Jing Lai

Journal of Electrochemistry

The Ru-Ir /Ti electrode as cathode to electrolysis the synthetic phenolic wastewater was studied. The effect of the initial chloride concentration on the electrolytic treatment result has been discussed. Experiment result shows that the electrochemical oxidation of phenol suits to one kinetics equation in given electrolytic time. If the initial chloride concentration in wastewater increases, the time of the electrochemical oxidation of phenol can be shorten, in other words the apparent rate constant is greater. The middle matters of electrochemical oxidation of phenol in the chloride system detected out by HPLC and GC-MS is mainly 1-chloro-phenol, 4-chloro-phenol, 2,4-dichloro-phenol, 2,6-dichloro-phenol, 2,4,6-trichloro-phenol, …

Diamond-Like-Carbon Film Prepared On Stainless Steel Substrates By Liquid Phase Electrochemical Deposition, Jing-Yong Du, Gui-Feng Zhang, Guo-Qing Li, Xiao-Duo Hou

Journal of Electrochemistry

Diamond-like carbon (DLC) films were deposited on stainless steel substrates at atmospheric pressure and low temperature (60 ℃) by electrolysis in a methanol solution with a pulseddirect current power supply. The morphology and microstructure of the resulting DLC films were analyzed using atomic force microscopy(AFM), scanning electron microscopy (SEM), Raman spectroscopy and Fourier transformation infrared spectrometry (FTIR). The experimental results show that the hydrogenated diamond-like carbon filmsare smooth and compact. Raman spectroscopy analysis confirmed the presence of a strongpeak at 1332.51 cm^-1, which is assigned to crystalline diamond. The deposition rate can be enhanced to 0.5 μm/h by …

Comparison Of The Electrochemical Reactivity Of Electrodes Modified By Carbon Nanotubes With Different Sizes, Guo-Feng Yang, Neng-Qin Jia, Zhi-Yong Wang

Journal of Electrochemistry

The electrochemical activity of multi-walled carbon nanotubes(MWNTs) with different sizes,including four different MWNTs with the same length and different diameter,two different MWNTs with the same diameter and different length has been assessed and compared.The various MWNTs modified electrodes were prepared by immobilizing the suitable amount of MWNTs onto a glassy carbon electrode,and their voltammetric responses to ferricyanide,uric acid and dopamine were examined.The corresponding cyclic voltammetric data was showed that the electrochemical and electrocatalytic activities are depended on the nanotube length.The electrochemical reactivity of short MWNT(S-MWNT) is better than that of long MWNT(L-MWNT),which may be mainly attributed to the existence of …

Mwnts Modified Gc Electrode For Hydrogen Peroxide Determination, Hong-Juan Wang, Chun-Mei Zhou, Hao Yu, Feng Peng, Jin-Kun Fang

Journal of Electrochemistry

A MWNTs modified GC electrode was constructed successfully to be used to detect hydrogen peroxide.Two methods of maximum anodic current of cyclic voltommogram and chronoamperometry were adopted to measure the concentration of hydrogen peroxide.The results show that the MWCNTs can enlarge the effective surface area of GC electrode and can enormously enhance the electron transfer.The sensitivity and correlation coefficient for hydrogen peroxide detection are 2.84 μA/mmol·L^-1,0.997 and 1.5 μA/mmol·L^-1,0.971 for cyclic voltammetry and chronoamperometry,respectively.The procedure of the two methods to detect hydrogen peroxide is simple,and the results obtained are satisfied.

Influence Of Electrolyte On The Preparation And Electrocatalytic Properties Of Pt/Gc Electrodes, Sheng-Pei Chen, Yan-Xin Chen, Tao Huang, Xiao-Wen Hou, Shi-Gang Sun

Journal of Electrochemistry

Influence of electrolyte on the electrocatalytic properties of Pt/GC electrodes for formic acid oxidation were studied by using cyclic voltammetry, SEM and electrochemical in situ FTIR spectroscopy. It has demonstrated that the surfaces of Pt/GC electrodes prepared in H₂SO₄ (Pt/GC1) or in HClO₄(Pt/GC2) are all composed of platinum particles, but which crystals are some differences in size and shape.Diameters of platinum particles on the surface Pt/GC1 are of 100~200 nm, and with spheral shape in the majority. The sizes of platinum particles on the Pt/GC2 electrode are larger in general,part of particles is of cube …

Study On The Electrochemical Machining Of Titanium Alloys Tc4 With The Method Of Uniform Design, Mei-Li Zhang, Di Zhu, Zheng-Yang Xu

Journal of Electrochemistry

For the electrochemical machining of titanium alloys,a passivating film tends to form on the machining surface,which holdbacks the process of machining;and some corrosive pittings can appear on the non-machining surface,which leading to the poor surface quality.So how to improve the machining surface quality,this is a hot problem in aerospace industries.An experiment plan has been made with the method of uniform design and the variance analysis has been carried out using the result data of the previous experiments.The experimental results show that an excellent machining surface with Ra 0.38 μm would be obtained in the electrolyte of 10% NaCl solution,4% Na …

Electrochemical Characteristics Of La0.7-XCeXMg0.3Ni2.4Co0.6(X=0～0.4) Hydrogen Storage Alloys, Ling-Ling Xiao, Yi-Jing Wang, Yi Liu, Jian-Sheng Cao, Da-Wei Song, Li-Fang Jiao, Hua-Tang Yuan

Journal of Electrochemistry

The effect of partial substitution of Ce for La on the structure and the electrochemical properties of the La_0.7-xCe_xMg_0.3Ni_2.4Co_0.6(x=0～0.4)hydrogen storage alloys have been investigated systematically.The result of X-ray powder diffraction(XRD) show that the alloys are all consisted of the LaNi₃ phase and the LaNi₅ phase.The maximum discharge capacity is decreased gradually with increase of the Ce contents,but the cycling life is improved obviously.

Fabrication And Performance Of Ni-Scsz Cermet Anode Modified By Coating With Gd0.2Ce0.8O2 For A Sofc, Ren-Zhu Liu, Bo Huang, Xiao-Feng Ye, Shao-Rong Wang, Jia-Di Cao, Huai-Wen Nie, Ting-Lian Wen

Journal of Electrochemistry

A Ni-scandia-stabilized zirconia(Ni-ScSZ) cermet anode modified by coating with nano-sized gadolinium-doped ceria(GDC,Gd_0.2Ce_0.8O₂) was prepared using a simple combustion process for the solid oxide fuel cell(SOFC) running on methane fuel. X-ray diffraction(XRD) and scanning electron microscopy(SEM) indicated that the surface of Ni-ScSZ was coated by nano-sized GDC particles(<100nm). Single cell testing showed that the 2.0%(by mass) GDC-coated Ni-ScSZ anode had better performance. The highest power densities of the cell with this anode were 825 and 848mW/cm² at 850℃ in humidified hydrogen and methane, respectively, whereas the corresponding values were 584 and 586mW/cm² for the cell with Ni-ScSZ anode.Electrochemical impedance spectra(EIS) illustrated that the cell with Ni-ScSZ anode exhibited far greater impedances than the cell with 2.0%(by mass) GDC-coated Ni-ScSZ anode.Then the …